Electricity is the flow of electrons (electric current) through a substance (conductor) from one object to another. Electricity can be Direct Current (DC) or Alternating Current (AC). DC is usually used for small appliances and in batteries. AC is produced by a rotating alternator and causes an oscillation of the electrons instead of a flow.
Current: the symbol is "I" and it is measured in amps or amperes. There are 1000 amperes in 1 amp.
Volts: the symbol is "V" is the electrical pressure, or sometimes referred to as the potential difference.
Resistance: the symbol is "R" and it is ability of the conductor to allow electricity to flow through it. Examples: rubber is a poor conductor. Metals, such as copper, are good conductors. Resistance is referred to as ohms.
Ohm's law states that: V (volts) = I (current/amps) x R (resistance) / ohms).
Power: the symbol is "P" and it is the wattage, or watts.
P(watts) = V X I
Short circuit: this is when the electrical flow takes a short cut. For example, a frayed wire touches another part of the appliance and takes the shortest route to its destination. This can be a cause of appliance fire, and electrocution.
Static electricity: the build up of electrons on a material with good insulation. Once something comes in contact with the static electricity it will move to that object. In some cases, if there are flammable gasses in the area there could be an ignition. Lighting is a natural form of static electricity.
Fuses: small tubes, with a wire connecting one end to the other, which will melt if too much current tries to passes through it. Designed to protect appliances, not people, from a power surge.
Circuit breaker: similar concept to a fuse, but it is a switch which can be easily reset. Again, designed to protect appliances, not people.
Residual Current Devices (RCD): designed to protect people. They will stop the flow of electricity much quicker if it senses an excess flow.
Reduced low voltage systems: a method of reducing the voltage that a device uses. Very common with hand power tools.
Double insulation: using two independent layers to insulate conductors to reduce chance of electrocution.